At the same time, what the complaint said was found on the attacker’s phone suggests he may have had access to the Islamic State’s secret chat rooms on the app Telegram. It is in these chat rooms, known as “channels,” that Islamic State followers congregate and post claims for attacks as well as share videos, including executions.
With numerous lawsuits filed against social media companies by the families of victims of recent Islamic State attacks, the group’s videos are often suspended within hours of being uploaded to YouTube, Twitter or Facebook. The group has increasingly turned to closed channels to share information.
Among the videos that investigators said they found on Mr. Saipov’s phone is one of the group’s most disturbing clips, showing the grotesque executions of prisoners forced to wear orange jumpsuits in an echo of the United States prison at Guantánamo Bay.
Although sanitized versions of these execution can be found on news sites, the full footage showing the killings is not readily available on the open web.
That the suspect was said to have these videos, as well as thousands of images of Islamic State propaganda suggests he may have had access to the group’s Telegram channels.
These channels cannot be searched outside Telegram, and can only be accessed with a Telegram key, a code that consists of a string of gibberish. An individual who gains access to the chat rooms, then, was probably invited by someone who shared the key.
These channels include online tutorials on how to carry out attacks. For example, the Lone Lions channel routinely posts step-by-step demonstrations showing how to make triacetone triperoxide, or TATP, the explosive compound used in nearly all Islamic State attacks in the West including in Paris, Brussels and Manchester, England. More important, these channels serve as digital watering holes, where ISIS scouts identify potential new attackers.
Numerous attacks in the last three years were carried out by recruits who made contact with Islamic State handlers on the Telegram app, and later migrated to encrypted, one-on-one chats.
Like any other app, Telegram can be deleted from a phone. The complaint does not state if investigators found the app on the two cellphones the suspect had at the scene, or if he erased the digital bread crumbs leading back to ISIS.